This invention relates to a bonding method and more particularly a method of bonding a cemented carbide surface to a metal surface.
Abrasive compacts are well known in the art and are used extensively in industry for the abrading of various workpieces. They consist essentially of a mass of abrasive particles present in an amount of at least 70 percent, preferably 80 to 90 percent, by volume of the compact bonded into a hard conglomerate. Compacts are polycrystalline masses having some direct particle-to-particle bonding. The abrasive particles of compacts are invariably superhard abrasives such as diamond and cubic boron nitride. Abrasive compacts are made under conditions of temperature and pressure at which the abrasive particle is crystallographically stable.
Abrasive compacts may be provided in a variety of forms such as circular discs, or segments thereof or fragments of other shapes.
Abrasive compacts may be bonded directly to a tool or shank for use. Alternatively, they may be bonded to a backing such as a cemented carbide backing which itself is bonded to the tool or shank. Abrasive compacts bonded to a cemented carbide backing are known in the art as "composite abrasive compacts".
Examples of abrasive compacts and composite abrasive compacts can be found in many patent specifications, for example British Patent Specification Nos. 1,489,130; 1,456,765 and 2,048,927 and U.S. Pat. Nos. 3,745,623; 3,743,489 and 4,224,380.
Composite abrasive compacts are used as cutting inserts for a variety of tools such as drill bits and mining picks. In many of these applications, it is necessary to bond the carbide backing firmly to the tool.
In other applications, the composite abrasive compact is bonded to a cemented carbide pin which is then located in a recess in the working surface of a drill bit and bonded thereto. One method which has been proposed for bonding the composite abrasive compact to the cemented carbide pin is described in European Patent Publication No. 0 090 657. This patent publication describes the bonding of the composite abrasive compact to a metal-containing substrate through a bonding layer comprising nickel, copper, cobalt, iron or an alloy containing one or more of these metals, bonding being achieved by means of solid state diffusion bonding. The metal-containing substrate is generally a cemented carbide substrate. It is to be noted that no working examples are provided of bonding a carbide surface to a metal surface.